I have reproduced below an article from the construction professional publication Solplan Review November 2008 because it was such a good article on this complicated subject. In 2023, Solplan Review is no longer in publication. For an animation on what is a rainscreen, follow this link.
But...
Skylights are basically windows that are not vertical, but usually closer to horizontal as they sit on top of the roof. Most are fixed but some open a bit for summer ventilation. There also exist roof windows which are basically skylights that open wide and are much more common in Europe where ...